Nanoparticles are particles having nanoscale particle sizes, and show optical, electrical and magnetic properties completely different from those of bulk materials due to a large specific surface area and the quantum confinement effect, in which energy required for electron transfer changes depending on the size of material. Accordingly, due to such properties, much interest has been concentrated on the applicability of nanoparticles in the catalyst, electromagnetic, optical, medical fields, and the like. Nanoparticles may be considered as intermediates between bulks and molecules, and may be synthesized in terms of two approaches, that is, the “top-down” approach and the “bottom-up” approach.
Examples of a method for synthesizing a metal nanoparticle comprise a method for reducing metal ions in a solution by using a reducing agent, a method for using gamma-rays, an electrochemical method, and the like, but in the existing methods, it is difficult to synthesize nanoparticles having a uniform size and shape, or it is difficult to economically mass-produce high-quality nanoparticles for various reasons such as problems of environmental contamination, high costs, and the like by using organic solvents.
Meanwhile, [Nano Lett., 2011, 11(3), pp 919-926] describes a method for preparing a core-shell particle comprising gold (Au) as a core and platinum (Pt) as a shell, but only discloses a method for preparing a core-shell particle by using platinum (Pt)-acetylacetonate (Pt-(acac)2), which is an organic metal compound, and an organic solvent, and does not describe a method for preparing a core-shell particle, which may solve environmental pollution and high cost problems.